Mix the crushed biscuits and melted butter in a bowl.
Place a chefs' ring onto a serving plate. Press the biscuit mixture firmly into the ring.
In a bowl, mix together the mascarpone, icing sugar and lemon juice. Spoon the mixture into the ring and smooth off the top using a palette knife. Remove the ring.
To make the raspberry coulis, blend the raspberries, icing sugar and lime juice in a mini-food processor and pass through a sieve.
To serve, drizzle the coulis over the cheesecake and garnish with a sprig of mint.